This invention relates to the processing of seismic data to render it more useful in interpreting the geological characteristics of the earth in the exploration for oil and gas deposits. Specifically, the invention relates to a novel method of displaying seismic data plotted in perspective form as a stereo pair with pre-determined parallax in order to identify the possible presence of hydrocarbon deposits or structural features associated with such deposits.
In seismic exploration, data is obtained by first creating an artificial disturbance along the earth by use of dynamite or the like. The resulting seismic waves travel downwardly in the earth and are reflected upwards from subsurface reflecting interfaces. The reflected waves are detected by arrays of sensitive devices called geophones located along the gound and recorded by reproducible means. The recorded waves, which contain information regarding the amplitude and arrival time of the reflected waves, information known to be useful in identifying possible hydrocarbon deposits, are known commonly as seismograms. In a typical seismic exploration, seismic energy would be recorded at uniformly spaced locations along a selected line of exploration to produce a series of seismograms along the line of exploration.
Methods of deriving information concerning geological characteristics of a subsurface formation from acquired seismic data are too numerous to mention. One method is to use the acquired seismic data to generate a perspective plot of the seismic data in which the effect of three-dimensional relief is obtained. In the practical application of generating a perspective plot of seismic data, three principal axes are selected and the data plotted with respect to the axes. One such selection of axes would involve the selection of arrival time of the seismic impulse along the x-axis, amplitude of the seismic impulse along the z-axis, and profile direction (profile direction being defined here as the location of the seismic geophones along the line of exploration) along the y-axis.
Once generated, the perspective plot of seismic data is a very useful tool in the interpretation of seismic data. Areas of geological interest are often recognizable upon examination of such a representation of seismic data, areas of interest usually being indicated by areas of abnormal levels of seismic energy on the seismic plot. A frequently sought-for situation which leads to such areas of abnormal seismic energy are commonly called "bright spots". However, seismic data evaluation based upon interpretation of such a seismic plot is unsatisfactory at the final stage of evaluation, i.e. during the identification of all bright spots indicative of areas of geological interest. At this point, while the standard seismic plot has identified the major locations where the seismic data indicates positive geological characteristics suggesting the presence of hydrocarbon deposits, there are still additional locations which also enjoy similar geophysical characteristics indicative of hydrocarbon deposits but which cannot be identified due to physical limitations inherent in the use of such seismic plotting methods.